The present invention describes a pressure vessel for storage of liquid and/or gaseous media under an operating pressure above atmospheric pressure, wherein the pressure vessel encloses a hollow space for storage of the medium, and is provided with at least one connection for filling and/or emptying. The invention further relates to a method for manufacturing such a vessel.
Liquid and/or gaseous media are normally transported in pressure vessels that are provided with a suitable construction resistant to leaks, diffusion or permeation of the medium stored, and the mechanical stresses of internal and external pressure respectively, as well as the further stresses of a mechanical, physical and chemical nature during operation.
By appropriate combination of polymers as a matrix with high strength fibres as reinforcement and by selection of a suitable reinforcing construction, customised material properties can be tailored to the component, according what is demanded. Pressure vessels manufactured from fibre plastic composites are equivalent in terms of pressure technology suitability to conventional steel or aluminium vessels, but offer, moreover, crucial advantages such as low weight, increased corrosion resistance and extreme resistance to fatigue.
Pressure vessels manufactured from fibre plastics composites with polymer matrix systems are known, and a large number of patents are in existence.
As an example, reference is made to European patent EP-0.810.081 A1 “Pressure Vessel and Method of Manufacture of Same”. This describes how a closed envelope layer that is composed of plastics is enclosed in a fibre winding procedure with a fibre plastics composite. A similar container concept is described in European patent EP0333013 A1 “Pressure Vessels”. In this case too, an envelope layer is surrounded with fibres such that the reinforcing shell withstands mechanical stresses.
Other known types of construction are described in patent documents DE 197 51 411 C1, DE 195 261 54 C2, EP 0.821.194.A2 (Mannesmann), EP 0.300.931 (Ullit), EP 0.333.013 A1 (ABB Plast), EP 0.550.951 A1 (Brunswick), EP 0.553.728 A1 (EDO) and WO 94/12396 (NGV Systems). The patent documents describe pressure vessels for gases and/or liquids, composed of plastics base bodies with differently constructed metal connection pieces, that with the exception of EP 0.333.013 A1 show the same patent content, while EP 0.333.013 A1 describes the processing technology of the winding method and respectively the laminate construction, and in particular optimum core geometry for optimum stress ratios in the fibre composite material.
In operation, the technologies described in the patents listed hereinabove have some shortcomings, in particular leaks in the area of the connector and high cost fabrication technologies.
The connector technology described in the EDO patents, for example, resulted in leaks in the area of the connector between the metallic connection piece and the plastics base body after a relatively short time in operation, with the result that the containers has to be taken out of service again. No known use has as yet been made, for example, of the NVG Systems patent, presumably because of the high cost fabrication technology. In the case of the design patented by Brunswick some containers failed during operation because of leaks (source: Powertech Labs/Vancouver).